Mapeamento tridimensional das alterações dentoesqueléticas mandibulares decorrentes do tratamento com os aparelhos de Herbst e Twin Block

Abstract

The present study aimed to assess the three-dimensional dentoskeletal mandibular changes in skeletal Class II growing patients treated with Twin Block and Herbst appliances. The sample was comprised by 22 Brazilian adolescents, both genders, malocclusion Class II division 1, at the peak of the pubertal growth spurt (CS3-CS4 stages of cervical vertebrae maturation). All patients were treated for 12 months at the Orthodontic Clinic, School of Dentistry, State University of Rio de Janeiro (FOUERJ). Twin Block group (TB) was composed of 15 patients (9 boys and 6 girls with mean ages of 12.3 and 11.9 years, respectively) treated with the Twin Block removable appliance. The Herbst group (HB) was formed by 7 youths (4 males and 3 females with mean ages 13.6 and 12.3 years, respectively) treated with the banded Herbst functional appliance, bonded to canines, premolars and molars. Cone Beam Computed Tomography (CBCT) were obtained for each patient in two time points: immediately before the start of the treatment (T1) and after 12 months of treatment (T2). Forty-four virtual 3D mandible models were built from the CBCTs for the whole sample. Superimpositions were made between T1 and T2 to evaluate the following specific regions of interest (SRI): condyles, mandibular ramus and corpus and lower central incisors. The greater distances in millimeters measured for each SRI between T1 and T2 were recorded and then compared using the Mann-Whitney test. The Wilcoxon test was used to compare the SRIs in pairs. Results showed both funcional appliances produced more esqueletal than dental effects. There were no differences between the groups for all regions analized (p < 0.05). Both groups presented in average, the most pronounced growth in condylar areas (right condyle = 6.12 mm in group TB and 7.01 mm in group HB; left condyle = 6.34 mm in group TB and 6.84 mm in group HB); small growth of the mandibular ramus (right ramus = 1.80 mm in group TB and 1.65 mm in group HB; left ramus = 1.86 mm in group TB and 1.66 mm in group HB); and the mandibular corpus showed the minor growth (0.54 mm both in groups TB and HB). The lower incisors presented a similar proclination in both groups (teeth 31 = 1.37 mm in group TB and 1.67 mm in group HB; teeth 41 = 1.34 mm in group TB and 1.5 mm in group HB). It can be concluded that patients treated with the Twin Block and Herbst appliances presented similar results concerning mandibular growth and lower incisor proclination.